Such marks assure consumers that the product is safe and meets performance standards, according to Trade and Industry Secretary Manuel Roxas II.
DTI has issued the warning over reports of the sale of defective or substandard Christmas lights which could overheat and result in unwanted fires.
The DTI, Roxas said, has intensified its information campaign on the use of Philippine National Standards (PNS) and the PS/ICC marks through a so-called "standards" blitz, targetting primary and secondary students of public and private schools in the National Capital Region (NCR).
The DTI is also strengthening its ties with retailers, dealers and distributors of products under mandatory certification in the second phase of its "standards" blitz.
Roxas said the DTI is also coordinating with various stores and shops to buy only from manufacturers and importers that were issued a PS license and ICC to sell only certified products.
Christmas lights are a DTI-regulated product.
Under the product certification scheme of the DTI’s Bureau of Product Standards, a regulated product or a product that is covered by the mandatory certification of the DTI-BPS, is submitted to the BPS testing center or any BPS-recognized laboratory for a series of test according to a specified PNS or a foreign standard, prior to distribution or selling in the market.